[uml-devel] Vmlinux - linux linking stages & /proc/kallsyms empty

[uml-devel] Vmlinux - linux linking stages & /proc/kallsyms empty

[BlaisorBlade]

Jeff, is there any good reason to first link everything in vmlinux and then 
link things properly in linux? Because I have reasons (i.e. bugs) against 
this.

--THE BUGS
**Symptom: /proc/kallsyms is empty. Any stack dump cannot contain the symbol 
names.

**Reason: This because the vmlinux link script is wrong (you rejected the 
patch I sent you time ago, was in the patchset). But kallsyms must contain 
the true addresses of the kernel symbols; since they change between vmlinux 
and linux (if they didn't change, the second step would be useless), they 
cannot be correct. I think that even System.map symbols do not match.

**Fix: So, we actually need to make vmlinux have the correct addresses, i.e. 
avoid the two-pass linking.

--HOW TO FIX THIS: 
You specify the -r flags for vmlinux, so you could as well pass the extra 
objects in and the right link script.

--WHY SHOULD WE BOTHER?
Because it is a fix and it is easy to fix.

Any comments?
-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729



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[uml-devel] Re: Vmlinux - linux linking stages & /proc/kallsyms empty

[Jeff Dike]

blaisorblade_spam@yahoo.it said:
> This because the vmlinux link script is wrong (you rejected the  patch
> I sent you time ago, was in the patchset). But kallsyms must contain
> the true addresses of the kernel symbols; since they change between
> vmlinux  and linux (if they didn't change, the second step would be
> useless), they  cannot be correct. I think that even System.map
> symbols do not match.

I didn't reject it so much as I put it aside for the moment because I didn't
understand it.

Your explanations, then and now, make sense, so I'm going to have another
look at it for my next 2.6 patch.

				Jeff



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Re: [uml-devel] Re: Vmlinux - linux linking stages & /proc/kallsyms empty

[BlaisorBlade]

Alle 23:38, martedì 30 marzo 2004, Jeff Dike ha scritto:
> blaisorblade_spam@yahoo.it said:
> > This because the vmlinux link script is wrong (you rejected the  patch
> > I sent you time ago, was in the patchset). But kallsyms must contain
> > the true addresses of the kernel symbols; since they change between
> > vmlinux  and linux (if they didn't change, the second step would be
> > useless), they  cannot be correct. I think that even System.map
> > symbols do not match.
>
> I didn't reject it so much as I put it aside for the moment because I
> didn't understand it.
>
> Your explanations, then and now, make sense, so I'm going to have another
> look at it for my next 2.6 patch.

Wait a moment (maybe you already understood this but I'm not sure): what I 
suggest *now* is much *more* than the patch I had at that time - that one was 
not enough (i.e. with that you get /proc/kallsyms full, but having wrong 
addresses)!

-- 
Paolo Giarrusso, aka Blaisorblade
Linux registered user n. 292729



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Re: [uml-devel] Re: Vmlinux - linux linking stages & /proc/kallsyms empty

[Jeff Dike]

blaisorblade_spam@yahoo.it said:
> Wait a moment (maybe you already understood this but I'm not sure):
> what I  suggest *now* is much *more* than the patch I had at that time
> - that one was  not enough (i.e. with that you get /proc/kallsyms
> full, but having wrong  addresses)! 

Yeah, but at least you're explaining things, which you didn't do with the
combo patch that I mostly applied last time.

I haven't checked whether you're explaining everything that I don't understand
yet :-)

				Jeff



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